Subtract 50/40 from 20/21, Solve 20/21

Subtract 50/40 from 20/21

1^st number: 20/21, 2^nd number: 1 10/40

20/21 - 50/40 is -25/84.

Find the least common denominator or LCM of the two denominators:
LCM of 21 and 40 is 840

Next, find the equivalent fraction of both fractional numbers with denominator 840
For the 1st fraction, since 21 × 40 = 840,
20/21 = 20 × 40/21 × 40 = 800/840
Likewise, for the 2nd fraction, since 40 × 21 = 840,
50/40 = 50 × 21/40 × 21 = 1050/840
Subtract the two like fractions:
800/840 - 1050/840 = 800 - 1050/840 = -250/840
After reducing the fraction, the answer is -25/84

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